Electronic devices such as selective call transceivers sometimes have a two-part housing that includes a base unit and a cover unit. The base unit typically houses most of the electronics, and the cover unit folds over the base unit. The cover unit typically contains a display.
A hinge mechanism is typically used to mechanically couple the cover unit to the base unit. The hinge mechanism allows the cover unit to be rotated from a closed position (in which the cover unit covers the base unit) to an opened position. Some electronic devices have a hinge mechanism that is biased in some way in order to allow opening of the cover unit with little friction to a pre-set, partially opened position and for maintaining the cover unit at that pre-set position. The typical hinge mechanism includes a cam member that rotates relative to a single spring on which the cam member bears. When the cover unit is manually opened somewhat, the force generated by the spring being deflected by the cam member urges the cover unit into a normally opened position and then tends to hold it in that position.
Electronic devices such as foldable wireless telephones typically have a pre-set, opened position for using the telephone, and they lack provision for remaining opened in any position other than the pre-set position. Some such electronic devices have a foldable housing that allows a user to open the cover unit to a plurality of positions more fully opened than the pre-set position. However, such known foldable housings disadvantageously lack provision for the cover unit to maintain itself at any of the more fully opened positions.
Electronic devices such as foldable portable computers typically lack a pre-set, opened position; instead, they have a frictional mechanism that allows the cover unit to be set at a plurality of positions with respect to the base unit.
Thus, what is needed is a frictional, hinge mechanism that has a pre-set position, and that allows low-friction rotation of the cover unit between the closed position and the pre-set position while also allowing constant high-friction rotation of the cover unit between the pre-set position and a multiplicity of positions more fully opened than the pre-set position. What is also needed is a frictional hinge mechanism that provides sufficient friction to prevent unwanted movement of the cover unit relative to the base unit at the pre-set position and also at any of a multiplicity of more fully opened positions, with the friction being apparent to the user only when the cover is rotated beyond the pre-set opened position.